RESTful Services vs. RESTful Interfaces
Many traditional middleware services do not fit into the RESTful style of development. An example is 2PC transaction management. Still, these services can benefit from having their distributed interface defined RESTfully. REST-*.org makes this distinction by defining RESTful services and RESTful interfaces.
RESTful Services
RESTful middleware services fit into the REST model of distributed development.
RESTful Interfaces
RESTful interfaces do not fit into the REST model of design and development. They are services that will benefit from having a RESTful interface defined, but will not be considered REST best-practices.